Construction and validation of a microprocessor controlled extracorporal circuit in rats for the optimization of isolated limb perfusion

Machine Perfusion Deters Ischemia-Related Derangement of a Rodent Free Flap: Development of a Model

INTRODUCTION

Machine perfusion can enable isolated support of composite tissues, such as free flaps. The goal of perfusion in this setting is to preserve tissues prior to transplantation or provide transient support at the wound bed. This study aimed to establish a rodent model of machine perfusion in a fasciocutaneous-free flap to serve as an affordable testbed and determine the potential of the developed support protocol to deter ischemia-related metabolic derangement.

METHODS

Rat epigastric-free flaps were harvested and transferred to a closed circuit that provides circulatory and respiratory support. Whole rat blood was recirculated for 8 h, while adjusting the flow rate to maintain arterial-like perfusion pressures. Blood samples were collected during support. Extracellular tissue lactate and glucose levels were characterized with a microdialysis probe and compared with warm ischemic, cold ischemic, and anastomosed-free flap controls.

RESULTS

Maintenance of physiologic arterial pressures (85-100 mmHg) resulted in average pump flow rates of 360-430 μL/min. Blood-based measurements showed maintained glucose and oxygen consumption throughout machine perfusion. Average normalized lactate to glucose ratio for the perfused flaps was 5-32-fold lower than that for the warm ischemic flap controls during hours 2-8 (P < 0.05).

CONCLUSIONS

We developed a rat model of ex vivo machine perfusion of a fasciocutaneous-free flap with maintained stable flow and tissue metabolic activity for 8 h. This model can be used to assess critical elements of support in this setting as well as explore other novel therapies and technologies to improve free tissue transfer.

Rhodococcus erythropolis septicaemia in a patient with acute lymphocytic leukaemia

Rhodococcus erythropolis rarely causes infection in humans. We report the second case of R. erythropolis septicaemia in a 7-year-old child. However, to our knowledge it is the first case in a patient with acute lymphocytic leukaemia who had been undergoing chemotherapy. The identification was performed using 16S rRNA gene sequencing. Even though R. erythropolis is rarely associated with human infections, it should be considered as a potential causative agent of bacteraemia, rather than overlooked as a contaminant.